Hi Tanu ,
You can use the following macro ( this is from another website , I forget which ) :
Private Sub Workbook_Open()
Due_date = #1/15/2012# 'January 15 , 2012 is the due date for renewing your licence
Todays_date = Date
Select Case (Due_date - Todays_date)
Case Is < 15: MsgBox "You have just 15 days to renew your licence", vbExclamation + vbOKOnly
Case Is < 45: MsgBox "You have 45 days to renew your licence", vbOKOnly
End Select
End Sub
Note that this code has to be in the ThisWorkbook object , in order to run.
Narayan